There has been proposed in recent years a compact and wearable image display apparatus to be head-mounted or spectacle-mounted. As an example of such image display apparatus, there has been known a device in which image light of an image displayed on a compact image display apparatus is guided through a transparent light guide member to the front of the eye of the observer so as to be displayed as an enlarged virtual image within the visual field of the observer (see, for example, Patent Literatures (PTL) 1, 2). A light guide member configured as described above, in particular, may be partially exposed from the casing, so as to be configured compact/light-weight in device size around the eye, and such compact and light-weight light guide member does not largely shield the visual field, making the image display apparatus available as a wearable device that can always be put on during use.